Perth’s MAX light rail project could be deferred further as the state government invests in other infrastructure and grapples with mounting debt.

This time last year, the West Australian government shelved the near $1.9 billion northeast Metro Area Express project for four years, citing ailing finances.

On Wednesday, an estimates hearing was told the Public Transport Authority was considering constructing a heavy-gauge rail line, also through the city's northeast.

That did not mean MAX had been axed, Premier Colin Barnett said, but he would not be drawn on whether the new completion timetable of 2022 would be met.

"That remains to be seen," he told reporters.

A rail link to the airport would come first, he said.

"MAX is not dead, but the government has made a decision to defer that - we just simply cannot afford to do two major projects together.

"The final form of MAX is to be determined, but that is something into the future.

"MAX is on hold. That's not a project the government is working on.

"We will go back to the project, reassess it."

MAX was a key plank of the Liberal party's 2013 election campaign.

The state government originally hoped the commonwealth would contribute half of the cost, but those hopes were dashed during the federal election campaign when Prime Minister Tony Abbott said the coalition wouldn't fund urban rail.